199 - Improved Progression-Free and Overall Survival with Radiotherapy Consolidation Post-Autologous Stem Cell Transplant in Patients with Relapsed/Refractory Aggressive Lymphoma with Pre-Transplant Partial Metabolic Response on FDG-PET
Presenter(s)
C. Abeyakoon1, D. Hodgson2, V. Murad3, H. Y. Yhim4, I. Gong1, J. Yi1, J. Kuruvilla1, M. Crump1, A. Prica1, V. Kukreti1, S. Bhella1, C. Yang1, T. Aoki1, D. Rodin2, N. Malik2, W. Wells2, U. Metser3, R. Kridel1, and A. Vijenthira1; 1Division of Medical Oncology and Hematology, Princess Margaret Cancer Centre, Toronto, ON, Canada, 2Division of Radiation Oncology, Princess Margaret Cancer Centre, Toronto, ON, Canada, 3Department of Medical Imaging, University Health Network, Toronto, ON, Canada, 4Division of Medical Oncology and Hematology, Jeonbuk National University Medical School, Jeonbuk, Korea, Republic of (South)
Purpose/Objective(s): Salvage chemotherapy followed by autologous stem cell transplant (ASCT) is a potentially curative procedure for patients (pts) with relapsed/refractory aggressive non-Hodgkin lymphoma (NHL). To improve long-term outcomes, the International Lymphoma Radiation Oncology Group (ILROG) guidelines recommend the use of radiotherapy (RT) after ASCT for pts with partial metabolic response (PMR) prior to ASCT. However, there are limited data supporting this recommendation in the PET era. Thus, our study objective was to evaluate whether consolidative RT after ASCT for pts with aggressive NHL with PMR (Deauville score (DS) 4 or 5) response to salvage therapy with one residual avid site, improves progression-free survival (PFS) and overall survival (OS), compared to pts not receiving consolidative RT.
Materials/Methods: Retrospective single center study of pts receiving ASCT between October 2013 - October 2024. Inclusion criteria: adults >18 years with histological diagnosis of aggressive NHL (B- or T-cell) who received salvage chemotherapy (anthracycline or platinum-based) with pre-ASCT PET demonstrating PMR (Lugano 2014 criteria) with one residual avid site. To prevent immortal time bias, we only included pts without progression >6 weeks following ASCT so they would have been eligible for RT. The exposure variable was consolidative RT. Outcomes included PFS defined from date of ASCT to date of progression/death and OS defined from date of ASCT to death. Survival probability and effect sizes were calculated using Kaplan-Meier method and cox regression. A sensitivity analysis was conducted including only pts without progression >90 days following ASCT. A two-sided p-value of 0.05 used to establish significance.
Results: We included 71 pts with PMR on pre-ASCT PET with only one residual avid site. Median age was 58 (interquartile range (IQR) 45-63) with 34% female patients. There were no differences in baseline characteristics between pts who received RT (N=42) versus those who did not (N=29). Median dose of RT was 30Gy (IQR 30-35Gy), typically over 15-20 fractions. During a median follow-up of 559 days (IQR 261-1625), pts receiving RT had a higher 1-year PFS (71% (95% CI 57-86) vs. 22% (95% CI 6-37), HR 0.22 (95% CI 0.11-0.42), p<0.0001) and OS (76% (95% CI 63-90) vs. 68% (95% CI 50-86), HR 0.45 (95% CI 0.20-0.996), p=0.049) than pts who did not. Both pre-ASCT DS4 and DS5 cohorts had improved 1-year PFS with RT; (DS4: PFS 79% (95% CI 64-94) vs. 24% (95% CI 6-42); DS5: PFS 46% (95% CI 13-79) vs. 14% (95% CI 0-40), p<0.0001). The primary outcome of PFS did not change in sensitivity analysis excluding pts in remission <90 days from ASCT.
Conclusion: RT consolidation after ASCT for PMR at one residual site appears to significantly improve PFS and OS, supporting the ILROG recommendations. Further analyses based on size of residual masses, site of post-ASCT relapse and reasons for not proceeding with RT will be presented at the meeting. Further work assessing pts in complete metabolic response is also ongoing.